Implant damage control by in-situ C doping during sige epitaxy for device applications

ABSTRACT

Some example embodiments of the invention comprise methods for and semiconductor structures comprised of: a MOS transistor comprised of source/drain regions, a gate dielectric, a gate electrode, channel region; a carbon doped SiGe region that applies a stress on the channel region whereby the carbon doped SiGe region retains stress/strain on the channel region after subsequent heat processing.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of co-pending U.S. patentapplication Ser. No. 13/113,107, filed on May 23, 2011, which is acontinuation of U.S. patent application Ser. No. 11/502,132, filed onAug. 9, 2006, now issued as U.S. Pat. No. 7,947,546 entitled Implantdamage control by in-situ C doping during SiGe epitaxy for deviceapplications, which claims priority at least under 35 U.S.C. 119(e) fromthe US provisional patent application:

Ser. No. 60/732,354, Filing date Oct. 31, 2005, entitled Implant damagecontrol by in-situ C doping during SiGe epitaxy for device applications,first named inventor Jin Ping Liu, Singapore, SG, Confirmation Number:5534. The entire contents of these related applications are incorporatedherein by reference in their entirety.

BACKGROUND OF INVENTION

1) Field of the Invention

Some example embodiments of the present invention relates to asemiconductor device with lattice-mismatched zone and fabrication methodthereof, and more specifically to a strained-channel transistorstructure and fabrication method thereof and more particularly to astrained-channel transistor structure and fabrication method comprisinga Carbon doped SiGe layer.

2) Description of the Prior Art

Size reduction of the metal-oxide-semiconductor field-effect transistor(MOSFET), including reduction of gate length and gate oxide thickness,has enabled a continuous improvement in speed performance, density, andcost per unit function of integrated circuits during the past fewdecades.

In order to further enhance performance of the transistor, stress/strainmay be introduced in the transistor channel to improve carrier mobilityto enhance performance of the transistor in addition to device scaling.There are several existing approaches to introducing strain in a channelregion of the transistor.

-   U.S. Pat. No. 6,844,227: Semiconductor devices and method for    manufacturing the same—Inventor: Kubo, Minoru; Mie, Japan-   US20040262694A1: Transistor device containing carbon doped silicon    in a recess next to MDD to create strain in channel Inventor:    Chidambaram, P R-   U.S. Pat. No. 6,190,975: Method of forming HCMOS devices with a    silicon-germanium-carbon compound semiconductor layer Inventor:    Kubo, Minoru; Mie, Japan-   U.S. Pat. No. 6,576,535: Carbon doped epitaxial layer for high speed    CB-CMOS—Inventor: Drobny, Vladimir F;-   U.S. Pat. No. 6,190,975 and US20020011617A1: semiconductor device    and method of producing the same—Inventor: KUBO, MINORU; MIE, Japan-   US20050035369A1: Structure and method of forming integrated circuits    utilizing strained channel transistors—Inventor: Lin, Chun-Chieh;    Hsin-Chu, Taiwan

However, there is a need to improve upon these methods.

SUMMARY OF THE INVENTION

Some example embodiments of the invention comprise a semiconductorstructure comprised of:

-   -   a MOS transistor on a substrate, the MOS transistor comprised of        source/drain regions, a gate dielectric, a gate electrode,        channel region;    -   a carbon doped SiGe region that applies a stress on the channel        region whereby the carbon doped SiGe region retain strain on the        channel region during subsequent heat processing.

A first example method embodiment, for forming a semiconductor devicecomprising the steps of:

-   -   providing a gate over a substrate;    -   etching S/D recesses in the substrate adjacent to the gate;    -   at least partially filling the S/D recesses with a carbon doped        SiGe layer;    -   forming source and drain regions about adjacent to the gate at        least partially in the carbon doped SiGe layer;    -   whereby the carbon doped SiGe layer puts a uniaxial strain on a        channel region under the gate.

A second example method embodiment for forming a semiconductor devicecomprising the steps of:

-   -   providing a gate dielectric layer, and a gate over a substrate;        the substrate comprised of silicon;    -   etching S/D recesses in the substrate adjacent to the gate;    -   partially filling the S/D recesses with a carbon doped SiGe        layer;    -   forming a top S/D Si-containing layer over the carbon doped SiGe        layer;    -   forming source and drain regions at least partially in top S/D        Si-containing layer; whereby the carbon doped SiGe layer puts a        uniaxial strain on a channel region under the gate.

A third example method embodiment for forming a semiconductor devicecomprising the steps of:

-   -   forming a carbon doped SiGe layer over a substrate; the        substrate comprised of silicon;    -   forming a top silicon layer over the carbon doped SiGe layer;    -   forming gate dielectric layer, a gate over the top silicon        layer;    -   etching S/D recesses in the substrate adjacent to the gate;    -   at least partially filling the S/D recesses with a silicon        containing layer;    -   forming source and drain regions in at least partially in the        silicon containing layer;    -   whereby the carbon doped SiGe layer puts a uniaxial strain on a        channel region under the gate.

A fourth example method embodiment for forming a semiconductor devicecomprising the steps of:

-   -   forming a center carbon doped SiGe layer over a substrate; the        substrate comprised of silicon;    -   forming a top silicon layer over the center carbon doped SiGe        layer;    -   forming a gate dielectric layer, and a gate electrode over the        top silicon layer;    -   etching S/D recesses in the substrate adjacent to the gate; and    -   at least partially filling the S/D recess with a S/D carbon        doped SiGe layer.

forming source and drain regions adjacent to the gate at least partiallyin the S/D carbon doped SiGe layer.

An aspect of all example embodiments is wherein the center carbon dopedSiGe layer has a Si atomic % between 68.8% and 84.9%;

-   -   a Ge atomic % between 15 and 30%;    -   a C atomic % between 0.1 and 0.2%.

An aspect of all example embodiments is the center carbon doped SiGelayer has a C concentration can be about between 1E19 and 1E20 atom/cc.

An aspect of all example embodiments further comprises; after formingthe carbon doped SiGe layer; annealing the substrate at a temperatureover 400 C.

A main advantage of the embodiments is that the SiGeC stressor regionsretain their stress on the channel region after heat processes greaterthan 400 C and especially after heat processes greater than 900 C.

The above and below advantages and features are of representativeembodiments only, and are not exhaustive and/or exclusive. They arepresented only to assist in understanding the invention. It should beunderstood that they are not representative of all the inventionsdefined by the claims, to be considered limitations on the invention asdefined by the claims, or limitations on equivalents to the claims. Forinstance, some of these advantages may be mutually contradictory, inthat they cannot be simultaneously present in a single embodiment.Similarly, some advantages are applicable to one aspect of theinvention, and inapplicable to others. Furthermore, certain aspects ofthe claimed invention have not been discussed herein. However, noinference should be drawn regarding those discussed herein relative tothose not discussed herein other than for purposes of space and reducingrepetition. Thus, this summary of features and advantages should not beconsidered dispositive in determining equivalence. Additional featuresand advantages of the invention will become apparent in the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of a semiconductor device according to thepresent invention and further details of a process of fabricating such asemiconductor device in accordance with the present invention will bemore clearly understood from the following description taken inconjunction with the accompanying drawings in which like referencenumerals designate similar or corresponding elements, regions andportions and in which:

FIGS. 1A through 1E are cross sectional views for illustrating astructure and method for manufacturing semiconductor device according toa first example embodiment of the present invention.

FIGS. 2A through 2E are cross sectional views for illustrating a methodfor manufacturing semiconductor device according to a second exampleembodiment of the present invention.

FIGS. 3A through 3F are cross sectional views for illustrating a methodfor manufacturing semiconductor device according to a third exampleembodiment of the present invention.

FIGS. 4A through 4B are cross sectional views for illustrating a methodfor manufacturing semiconductor device according to an fourth exampleembodiment of the present invention.

FIG. 5A, shows rocking curves of SiGe layers without C in-situ doping(control cell) for a) as grown, c) after B implantation and hightemperature anneal; Rocking curves of SiGe layers with C in-situ doping(invention) for b) as grown, and d) after B implantation and hightemperature anneal.

FIG. 5B contains cross-sectional/plan-view TEM images of SiGe layersafter B implantation and high temperature anneal for a)/c) without andb)/d) with C in-situ doping (invention's cell).

FIG. 5C contains cross-sectional TEM images of SiGe layers after Asimplantation and high temperature anneal for a) without and b) with Cin-situ doping (invention's cell).

FIG. 6A is a table showing the results of an experiment involving theexample embodiment's C doped SiGe layers.

FIG. 6B is a graph of some results of an experiment involving theexample embodiment's C doped SiGe layers.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS Overview

Non-limiting example embodiments of the invention form carbon doped SiGestressor layers (SiGeC) that retain their strain after ion implantsand/or heat cycles. The carbon doped SiGe stressor layers can be used inMOS transistors to put stress on the MOS channel regions to improvetransistor performance. The embodiments' carbon doped SiGe stressorlayers (SiGeC) can also reduce Ion implant damage in adjacent, proximateor overlaping doped regions. Preferably the carbon doped SiGe stressorlayers are formed using an epitaxial process. The SiGeC regions can puta uniaxial stress on the MOS channel regions. A point of some exampleembodiments is that the C in the SiGe layers enables the SiGeC layer tomaintain stress on the substrate even after subsequent heat cycles, suchat over 400 C and especially over 900 C. The inventors have found thatSiGe loses it's stress after heat cycles/anneals. The embodiment's C inthe carbon doped SiGe stressor layers helps the SiGeC layer retainstress even when annealed at temperature between 400 C to 1300 C andmore preferably between 900 and 1090 C and more preferably above 900 C.

Four example embodiments are described below.

Terminology:

-   SiGeC means carbon doped silicon germanium (e.g.,    Si_(1-x-y)Ge_(x)C_(y)) (Silicon germanium carbon alloy).-   Junction depth or depth of doped region—defined as depth from    substrate surface where the n and p concentration are about equal.    Schematically, the drawn junctions represent the boundary at which    the n-type and p-type dopant are equal. These can be adjusted with    adjusting the implant profiles either with different implant energy,    dose and species type. In general, in the figures, the junction    depth of the doped regions corresponds to a dopant concentration    about 1E17 atom/cc.-   SDE—source drain extension

I. First Embodiment a PMOS FET with S/D Regions in a SiGeC Region FIG.1D

An example embodiment comprises a PMOS transistor with one or more ofthe doped source/drain regions comprised at least partially with theSiGeC region. The SiGeC region can effectively put a uniaxialcompressive strain on the PMOS channel.

A first example embodiment is shown in FIG. 1D.

FIG. 1D shows a substrate with carbon doped SiGe regions 36 in thesubstrate 10 adjacent to the gate structure 20 22 of a PMOS transistor50P. The PMOS transistor 50P can be comprised of a gate dielectric,gate, spacers, source/drain (S/D) regions and source-drain extensions(SDE) regions. The transistor can further comprise other elements suchas Halo or pocket implants (not shown).

FIG. 1C shows the source/drain regions 40 can be formed totally withinthe Carbon doped SiGe regions 36. The source/drain regions 40 can beformed by implanting p-dopants such as B or BF2 in the substrate. Theimplants can create End of range defects (EOR defects) or other defects44 as shown in FIG. 1C.

The SiGeC layer 36 preferably has about the following concentrations:

Si atomic % between 68.8% and 84.9% (tgt=74.85)

Ge atomic % between 15 and 30% (target=25%)

C atomic % between 0.1 and 0.2% (target=0.15%)

In another measurement units, the C concentration can be about between1E19 and 1E20 atom/cc.

The SiGeC layer can have these concentrations and concentration profilesin all embodiments (e.g., PMOS and NMOS).

The SiGeC layer 36 can have an about constant C concentration or canhave a C concentration that varies between about 0.1 and 0.1 with depth.

The carbon doped SiGe layer is preferably formed by a selective epitaxyprocess, such as a LPCVD process.

The SiGe regions reduce the defects from the S/D ion implant (I/I) andfrom any other implants such as a halo implant or pocket implant (notshown).

A. First Embodiment Example Method—C-doped SiGe S/D Fill Regions

A non-limiting example method for the 1st example embodiment is shown inFIGS. 1A to 1E. It is understood that there are alternative methods toform the 1st example embodiment and this example does not limit theembodiment.

FIG. 1A

FIG. 1A shows a cross sectional view of a gate structure 20 22 24 over asubstrate 10. In this non-limiting example, the Tx is a PMOS 50P.

A gate structure can be comprised of a gate dielectric 20, a gateelectrode 22, and spacers 24. A MOS transistor 50P can be comprised ofthe gate structure 20 22 24, a channel region under the gate electrode22 and gate dielectric 20 in the substrate 10.

The substrate 10 can be a silicon or SOI substrate. The upper substratesurface is preferably comprised of Si and can have a (100), (110), or(111) crystal orientation or other orientations and preferably a (100)orientation.

Isolation regions 18 can be formed in the substrate and can separatePMOS regions 11 and NMOS regions 12. (see FIG. 1E).

We can form LDD regions (or SDE) 26 in the substrate adjacent the gatebefore the spacers 24 are formed.

We etch S/D trenches 30 in the substrate 10 adjacent to the gatestructures. We can use a trench resist mask 28 and the gate structuresand the isolation regions as etch masks. We can remove the resist maskafter the trenches are formed. The trench can have a depth between 700and 2000 angstroms.

FIG. 1B

As shown in FIG. 1B, we form a SiGeC layer 36 at least partially fillingthe S/D recesses/trenches 30. The SiGeC layer 36 is preferably formed bya selective epitaxial process that can at least fill the S/Drecesses/trenches 30.

FIG. 1C

As shown in FIG. 1C, we preferably implant dopant ions to form thesource and drain (S/D) regions 40. For this PMOS example, the ions arep-type such as B, or BF2.

The S/D implant can form end of range (EOR) defects (and other defects)44 near the bottom and below of the S/D regions 40.

Preferably the SiGeC region 36 has a lower depth at least 2.0 to 3.0 Rp(projected range) of the S/D implant. This depth helps ensures that thedefects 44 are contained mostly within the SiGeC region 36 can reducedefects.

FIG. 1D

FIG. 1D shows the structure after an anneal. The defects are reduced bythe SiGeC layer 36. The defects are reduced especially by the C in theSiGeC layer. The SiGeC layer preferably puts a uniaxial compressivestrain (C) on the channel region.

After all heat processing, the SiGeC layer preferably has a depth belowthe bottoms of the Source and drain regions and preferably the sourceand drain regions are substantially contained in the SiGeC layers 36.

The embodiment's carbon (C) in the SiGeC layer helps the SiGeC layerretain stress even when annealed at temperature Between 400 C to 1300 Cand more preferably between 900 and 1090 C.

FIG. 1E

FIG. 1E shows a cross sectional view of both PMOS TX 50P and NMOS Tx 50Nformed on a substrate. The SiGeC layer 36 was only formed in the PMOSregion 11. The SiGeC region 36 puts a compressive stress on the PMOSchannel thereby improving the PMOS performance. The NMOS region 12 canbe masked during the S/D recess etch in the PMOS region 12.

The NMOS Tx 50N can be comprised of: gate dielectric 20N, gate 22N,spacers 24N, LDD regions 26N, Halo region 28N, S/D region 40N and Pwell14.

Preferably the SiGeC region 36 has a depth after all anneals (finalproduct stage) that is at least 1% deeper and more preferably at least10% deeper than the final total depth (measured from the top SiGeCsurface) of the source and drain regions 40 and more preferably between10% and 20% deeper than the final total depth (measured from the topSiGeC surface) of the source and drain regions 40.

B. Uniaxial Strain

In some embodiments, because the SiGeC regions are positioned adjacentto the Gate only in the direction from source to drain (not along thelength of the channel), the SiGeC regions impart effectively a uniaxialstress on the channel.

For example in this embodiment shown in FIG. 1D, the SiGeC layer 36 putsa compressive stress/strain (C) on the PMOS channel region below thegate 22 thus improving hole mobility and PMOS transistor performance.Because the lattice constant of the SiGe is larger than that of Si, thechannel region between the two SiGe source/drains is placed undercompressive stress (C).

II. Second Example Embodiment SiGeC and Top Si Layer in S/D Recess

A second example embodiment comprises a NMOS transistor with the SiGeCregion under and spaced from the source/drain (S/D) regions. The SiGeCregion puts at least a tensile strain on the NMOS channel. The S/Dregions are preferably substantially in a Si containing layer over theSiGeC regions.

Referring to FIG. 2E, a SiGeC region 237N is formed in a S/D recess 230N(see FIG. 2C) adjacent to the NMOS gate structure 20N 22N.

A top S/D silicon layer 238N is formed over the SiGeC region 237N. Thesilicon layer can be comprised substantially of silicon. The siliconlayer can be doped with N type dopants or undoped.

S/D regions 240N are at least partially formed in the silicon layer 238Nand possibly at least partially formed in the SiGeC region 237N.

The SiGeC region 237N preferably puts a uniaxial tension stress on theNMOS channel region.

The SiGeC region 237N helps reduce defects from the S/D I/I.

In addition, the carbon (C) in the SiGeC region 237N helps the SiGeCregion 237N retain it's stress during subsequent processes, such as theS/D anneal.

A. Uniaxial Strain

Because the SiGeC regions 237N are positioned adjacent to the gate onlyin the direction from source to drain (not along the length of thechannel), the SiGeC regions effectively imparts a uniaxial stress on thechannel. This is not significantly a biaxial strain device.

For example in this embodiment shown in FIG. 2E, The SiGeC layer 237Nputs a tensile stress/strain (T) on the NMOS channel region thusimproving electron mobility and NMOS transistor performance.

B. Example Method for the Second Embodiment

A non-limiting example method for the second example embodiment is shownin FIGS. 2A to 2E. It is understood that there are alternative methodsto form the 2nd example embodiment and this example does not limit theembodiment.

FIG. 2A

FIG. 2A shows a substrate 10 with a NMOS region 12 and a PMOS region 11.A NMOS gate structure 20N 22N 24N is formed over the NMOS region 12. TheNMOS gate structure can comprise a NMOS dielectric layer 20N, A NMOSgate 22N and NMOS spacers 24N.

A PMOS gate structure 20 22 24 is formed over the PMOS area 11. The PMOSgate structure can comprise a PMOS dielectric layer 20, A PMOS gate 22and NMOS spacers 24.

The PMOS region 11 can comprise an optional N-well 13. The NMOS region12 can comprise an optional P-Well 14.

FIG. 2B

FIG. 2B shows a N-S/D recesses 230N formed adjacent to the N-gatestructure. A resist layer 228 can cover the PMOS region 11 or havingopenings over the NMOS region 12. The resist layer is removed after therecess etch. The trench can have a depth between 700 and 2000 angstroms.

FIG. 2C

FIG. 2C shows a NMOS S/D SiGeC layer 237N formed to at least partiallyfill the N-S/D recess. The S/D SiGeC layer 237N can be formed using anselective epitaxial process. The S/D SiGeC layer 237N can have the sameconcentrations as discussed above in the first embodiment.

FIG. 2D

FIG. 2D shows a top NMOS Si containing S/D layer 238N formed over theSiGe C layer 237N. The top N-Si S/D layer 238N is preferably comprisedsubstantially of crystalline silicon.

The top N-Si S/D layer 238N can have a thickness between 500 and 1000angstroms.

The N-S/D SiGeC layer 237N can have a thickness between 200 and 1000angstroms.

The SiGeC layer 237N preferably puts a Tensile stress (T) on the NMOSchannel for example, roughly between about the SDE regions.

The SiGeC layer 237N preferably has the following concentrations

Si atomic % between 68.8% and 84.9% (tgt=74.85)

Ge atomic % between 15 and 30% (target=25%)

C atomic % between 0.1 and 0.2% (target=0.15%)

FIG. 2E

FIG. 2E shows S/D regions 240N are formed adjacent the gate structure atleast partially in the silicon containing layer 238N. The S/D regions240 are preferably formed by an implant process. Preferably the EORregions from the S/D implant (before anneal) are located close to theSiGeC region so the EOR defects can be reduced by the SiGeC region.

The S/D regions 240N are least partially formed in the silicon layer238N and possibly at least partially formed in the SiGeC region 237N.

In an option, after all anneal steps, the S/D regions 240N aresubstantially contained within the Si containing layer 238N. In anotheroption, all anneal steps, the S/D regions 240N are substantiallycontained within the Si containing layer 238N and the SiGeC layer.

The SiGeC region 237N preferably puts a uniaxial tension stress on theNMOS channel region.

The SiGeC region 237N helps reduce defects from the S/D Ill.

In addition, the carbon (C) in the SiGeC region 237N helps the SiGeCregion 237N retain it's stress during subsequent processes, such as theS/D or silicide anneal.

III. Third Example Embodiment SiGeC Region Under the Channel Region of aMOS tx

FIGS. 3E and 3F show an example embodiment comprising a SiGeC regionunder the channel region of a MOS tx. The SiGeC region puts a stress onthe channel region of the MOS transistors. In this embodiment the S/Dregions preferably are formed in silicon layers, not in SiGec. Dependingon the configuration of the SiGeC layer, a uniaxial compressive or atensile stress can be placed on the channel regions.

A. Method for the Third Example Embodiment

A non-limiting example method for the 3^(rd) embodiment is shown inFIGS. 3A to 3E. It is understood that there are alternative methods toform the 3^(rd) example embodiment and this example does not limit theembodiment.

Depending on the device geometry, the stress can be tuned to be largelyuniaxial or biaxial. By tuning the stress tensor, (e.g., compressive ortensile) one can use the film for either N or P MOS or both.

As shown in FIG. 3A, a semiconductor substrate 10 is provided havingspaced isolation regions 18 defining at least a PMOS region 11 and aNMOS region 12.

As shown in FIG. 3B, we etch back the silicon containing substrate 10surface to form stressor recesses 15 16. The stressor recesses can havea depth between 500 and 1500 angstroms. We can use the isolation regions18 as an etch mask.

As shown in FIG. 3C, we can selectively form a SiGeC layer 301 301N overthe substrate surface. The PMOS SiGeC layer 301 and the NMOS SiGeC layer301N can be formed in 2 separate steps so that their compositions aredifferent. The areas that we do not want the SiGeC can be covered. Thatis we can tune SiGeC layers 301 301N to have the proper compression andtensile stress for the type devices (PMOS or NMOS) we are forming.

The SiGeC layer preferably has thickness between 50 and 100 nm. (500 and1000 angstroms). The Si & Ge & C concentrations in the SIGE C layer 301301N can be as described above in the other embodiments.

Next an upper channel Si-containing layer 303 303N is formed over theSiGeC layer 30 301N. The Si-containing layer 303 303N preferably hasthickness between 20 and 50 nm (200 and 500 Angstroms). The siliconcontaining layer 303 303N can consist substantially of crystallinesilicon. The channel region is preferably at least partially in theupper channel Si-containing layer 303 303N. In an aspect, the channelregion is fully in the upper channel Si-containing layer 303 303N.

An optional N-Well 13 can be formed at any time. An optional P well (notshown) can also be formed at any time.

Referring to FIG. 3D, we form S/D recesses 310 310N in the silicon layer303 303N, the SiGeC region 301 301N and possibly in the substrate 10.

Referring to FIG. 3E, we fill the PMOS S/D recesses 301 and NMOS S/Drecesses 310N with a silicon continuing material 320 320N and preferablysubstantially with Si or crystalline Si. In an aspect, the PMOS S/Drecess 301 are filled with a different material than the NMOS S/Drecesses. In another aspect, either the PMOS S/D recess 301 or the NMOSS/D recess 301N or both are filled at least partially with SiGe orSiGeC. In an aspect, the Si material is comprised of 2 layers, a bottomSiGeC layer and an top Si layer. This could allow further tailoring thestress, mobility and performance of the NMOS and PMOS regions.

Referring to FIG. 3F, we perform a S/D implant to form PMOS S/D regions40 in some combination of the silicon region, SiGeC region and thesubstrate.

The S/D implant comprises implanting Boron, Bf2, As, P or Sb ions intothe substrate.

We can form NMOS S/D regions 40N adjacent to the NMOS gate.

Next, halo implants can be performed to form NMOS halo regions 28N andPMOS halo regions 28. Masking steps (not shown) can be used to mask theproper areas.

In one aspect, the entire LDD (or SDE) region 26 is contained in theupper channel Si-containing layer 303 303N. and the silicon continuingmaterial 320 320N.

In this example, a NFET is formed in the NMOS region 12 and a PFET isformed in the PMOS region 11. There are other combinations. Theembodiment's SiGeC may only be formed in the NMOS region and the PMOSregions can be standard devices or any of the other embodiments in thisdisclosure.

Non-Limiting Review of Example Embodiment SiGeC Layer Under the Channel

The SiGeC layer 301 301N under the PMOS or NMOS channel provides defectgettering from the implanted doped regions (e.g, SDE and S/D and Halo)and maintains stress on the channels from the SiGeC regions 301 301N.

Depending on the device geometry, the stress can be tuned to be largelyuniaxial or biaxial. By tuning the stress tensor (SiGeC regions), onecan use the file for either NMOS or PMOS devices or both.

Depending on the SiGeC stressor composition and geometry, the PMOS SiGeClayer 303 can put compressive stress on the PMOS channel. Depending onthe SiGeC stressor composition and geometry, the NMOS SiGeC layer 303Ncan put a tensile stress on the NMOS channel.

Other steps to form a completed device can be performed in any otherusing processes known by those skilled in the art.

IV. Fourth Example Embodiment

In a fourth example embodiment shown in FIGS. 4A and 4B, a first (or acenter) SiGeC or SiGe layer 303 303N is formed under the channel of aMOS transistors. A second SiGe or SiGeC layer 420 420N is formed in S/Drecesses 410 410N. The second (or center) SiGeC or SiGe layer (or S/DSiGe or S/D SiGe C layer) 420 420N can be under the doped S/D regions,contained within the S/D region, or partially overlap the S/D region orany combination of the above. Preferably the S/D SiGE or S/D SiGe Clayer 420 420N fills the entire S/D recess 410 410N and extends belowthe S/D regions.

An example method for the fourth embodiment begins as described abovefor the third embodiment and shown in FIGS. 3A to 3C. Note that the PMOSSiGeC layer 301 and the NMOS SiGeC layer 301N can be formed in 2separate steps so that their compositions are different. Next, referringto FIG. 4A, we etch S/D recesses 410 410N adjacent to the gatestructures.

Referring to FIG. 4B, we fill the S/D recesses 410 410N at leastpartially with a SiGeC or SiGe layer 420 420N. FIG. 4B shows the aspectwhere the SiGeC substantially fills the S/D recesses. The PMOS S/Drecesses 410 and NMOS S/D recesses 410N can be filed with SiGeC or SiGein separate steps so that the second (or center or SD) SiGeC or SiGelayers 420 and 420N can have different compositions. The second (orcenter or S/D) SiGeC or SiGe layers 420 and 420N can have differentcompositions that create different amounts and types (compressive ortensile) of stress in the respective channels.

Next, the devices can be completed by for example, forming S/D regions40 40N, and Halo implants (not shown).

Depending on the device geometry, the stress can be tuned to be largelyuniaxial or biaxial. By tuning the stress tensor, one can use the filmfor either N or P MOS or both.

For the PMOS Tx, the S/D SiGeC 420 and channel SiGeC 301 can put acompressive stress on the PMOS channel.

For the NMOS Tx, the S/D SiGeC 420N and channel SiGeC 301N put a tensilestress on the NMOS channel.

Another possible aspect of the fourth embodiment is shown in FIG. 2E,where the SiGeC layer 237N partially fills the S/D recess and a siliconlayer 240N is formed over the second SiGeC region 237N. The aspect mightbe used in a NMOS transistor.

A. Examples Impact of In-Situ C Doping on Implant Damage and StrainRelaxation of Epitaxial SiGe Layer on Si

In this example, implant damage and strain relaxation in thin epitaxialSiGe layers on Si (001) and their dependence on in-situ C doping inepitaxial SiGe are studied. For a 65 nm SiGe layer with ˜25% Ge,conventional implants used for p-MOS S/D, halo and extension led tosignificant implant damage and strain relaxation. Two defect bands wereobserved, one close to the surface and the other at SiGe/Si interface.In-situ C doping (10¹⁹⁻²⁰/cm³) was found to eliminate the implant damageclose to SiGe/Si interface area and prevent significant strainrelaxation.

Here we study the implant damage and strain relaxation in thin epitaxialSiGe films (later referred to as SiGe) and in-situ C doped SiGe films(later referred to as SiGeC) on Si (001) substrates. We show that for a65 nm SiGe layer with ˜25% Ge, conventional implants used for p-MOS S/D,halo and extension lead to significant implant damage and strainrelaxation. Two defect bands are observed: one is close to the surfaceand the other is at SiGe/Si interface. In-situ C doping (10¹⁹⁻²⁰/cm³) isfound to eliminate the implant damage close to SiGe/Si interface areaand prevent significant strain relaxation.

Epitaxial SiGe and SiGeC growth was performed on a commerciallyavailable LPCVD system. An additional C precursor was used for in-situ Cdoping under otherwise identical conditions. After epi growth, waferswere implanted using typical conditions for P-MOS S/D, halo, andextensions. Typical results are presented here from two differentimplants: 1) B implant with energy of several KeV and dose about10¹⁵/cm², and 2) As implant with energy of tens of KeV and dose of10¹³/cm². After implantation, wafers were rapid thermal annealed at hightemperature (>1000 C). The strain relaxation and implant damage werecharacterized by high-resolution XRD and cross-sectional TEM. FIG. 5Ashows XRD results for (a) as grown SiGe layers, (b) as grown SiGeC, and(c) as B-implanted and annealed SiGe as well as (d) as B-implanted andannealed SiGeC. Well defined thickness fringes are seen in the as-grownfilms (FIG. 5A (a) and (b), indicating little strain relaxation andsmooth interface. Fitting the rocking curve for the SiGe layer in FIG.5A(a) using commercially available software gives a Ge composition of24.3% and a thickness of 65 nm. Assuming the same Ge composition as inSiGe layer, the substitutional C composition is determined to be 0.07%by fitting 5A(b) and using a non-linear relationship between C contentand the lattice constant. This result is close to SIMS data indicating˜100% substitutionality. After B implant and anneal, the (004) peaklocation for SiGe layer moves to lower angle and the thickness fringesdisappear, indicating significant strain relaxation. The (224)reflection shows a broad peak, consistent with (004) reflection results.With no appreciable Ge interdiffusion during the anneal (AES results notshown), i.e., no change in Ge composition in the SiGe layer, a strainrelaxation of ˜70% is calculated from (004) peak shifts shown in FIGS.5( a) and (c). Compared to SiGe layer, SiGeC layer shows less (004) peakshift to lower angle, and (224) reflection shows a sharp peak above abroad peak (FIG. 1( d)). The strain relaxation degree, if determinedfrom (004) peak shift, is ˜13%. The sharp peak in (224) reflection (FIG.5A (d), solid line), however, corresponds to a fully coherent SiGelayer, indicating nearly 0% strain relaxation. The apparentinconsistency can be explained by the microstructure of the epi filmsrevealed by the TEM results shown in FIG. 5B.

For the implanted SiGe layer, we observed two bands of defects (FIG. 5B(a)), one close to the surface and the other at the SiGe/Si interface.The defects in the surface band are of the stacking fault tetrahedraltype, while the dense arrays at the interface are misfit dislocations.The dominating features in the plan-view TEM (FIG. 5B (c)) are Moiréfringes, which obscure any contrast from the defects in either thesurface or interface bands seen in FIG. 5B (a). Unlike the SiGe layer,the SiGeC film displays only the dense band of defects at the surface(FIG. 5B(b)). A well-ordered array of misfit dislocations exists at theSiGeC/Si interface (FIG. 5B(d)). The array is of low density such thatthe misfits are not seen in a random TEM cross section (FIG. 5B(b)).

We now propose an explanation on the strain relaxation behavior shown inFIG. 5A. The TEM results (FIG. 5B) show that in addition to theinterface defects which normally cause relaxation in SiGe/Siheteroepitaxy system, there are surface defects that can relieve thestrain in the top part of epilayers. This non-uniform strain relaxationacross the depth of epilayers can be seen from the slightly asymmetrical(004) peak and the broad peak together with the sharp peak in the (224)reflection (FIG. 1( d)). From the spacing of these misfit dislocationsin SiGeC layers (FIG. 5B, (d)), the strain relaxation degree caused byinterface defects is determined to be ˜1%, consistent with the positionof the sharp (224) peak observed in FIG. 5A(d). Thus the (004) peakshift in FIG. 5A (d) mostly comes from the additional strain relaxation,estimated to be ˜12%, from the surface defects. Because of thesimilarity of the surface defects observed between SiGe and SiGeClayers, we can assume the same strain relaxation degree, ˜12%, is causedby the surface defects. This is relatively small, compared to theoverall strain relaxation, ˜70% for the SiGe epilayer. The non-uniformstrain relaxation along the depth in SiGe layers is thus not clearlyresolved in our (004) and (224) reflections.

Very interesting, we found very similar results on the implant damageand strain relaxation in the SiGe and SiGeC layers for the more-damagingAs implants. As can be seen from the TEM results shown in FIG. 5C, forSiGeC, there is a surface defective layer, which is thicker due to thedeeper projected range for the implants. The interface again is cleanwithout many defects, indicating small degree of strain relaxation atthe interface, consistent with ∥9% strain relaxation determined from XRDresults (not shown). For the SiGe layer, however the film becomes quitedefective across the depth. It seems the surface defect band isconnected with the interface defect band, as observed in the B-implantedcases discussed earlier. The dense array of defects causes 85% strainrelaxation in SiGe layer determined by XRD (not shown).

A hypothesis is that dislocation loops generated by implants in SiGelayer and Si substrate can move to SiGe/Si interface and form misfitdislocations, causing more strain relaxation than SiGe layer grown on Siwithout implants under the same thermal budget. This hypothesis isconsistent with the high strain relaxation degree we observed here forimplanted SiGe epi layers and with the fact that we found little strainrelaxation for similar SiGe epi layers on Si with high temperatureanneals alone. A small little amount of C has been shown to eliminatethe EOR defects for implants in Si, which has been attributed to C atomsacting as Si interstitial sinks. A similar mechanism seems to beoperating for epitaxial SiGe layers. The suppression of EOR defectsinhibits the nucleation of misfit dislocation for such thin SiGe layerand thus prevents strain relaxation. Near the surface however thedefects are still formed as in SiGe layer, which may be due to theinefficiency of Si interstitial sinks or too many displaced Si, becauseof the shallow implant conditions used.

In summary we have shown that for a 65 nm SiGe layer with ˜25% Ge,conventional implants used for p-MOS S/D, halo and extension lead tosignificant implant damage and strain relaxation. Two defect bands areobserved: one is close to the surface and the other is at SiGe/Siinterface. Surface defects cause additional strain relaxation in the toppart of the epi layers. In-situ C doping (1E19 to 1E20/cm³) is found toeliminate the implant damage close to SiGe/Si interface area and preventsignificant strain relaxation.

B. Example 2-C Helps SiGe Retain Stress after Anneals

Test wafers were prepared using the following flow:

-   -   Grow SiGe(C) epi with a C concentration about 1.5 atomic % (1E19        to 1E20/cm³)    -   Implant    -   RTA at T greater than 1000 C    -   (stress measurement done after each step)

FIG. 6A shows the results in tables 1, 2, 3 and 4.

FIG. 6B shows a graph of percentage of Stress retained vs C for the 4I/i conditions.

Some conclusion that we can draw from FIG. 6A and FIG. 6B.

-   -   1) C helps SiGe retain stress for all 4 implant conditions    -   2) As implant gives the worst impact on stress loss followed by        B S/D implant and then by BF2 implants.    -   3) It seems implant-induced damage is the major contributor to        stress loss although film thickness may be slightly thicker than        critical thickness.        CN=0.5 sccm is about C concentration in the SiGec layer of about        3E19 Atoms/cc        CN=1.2 sccm is about C concentration in the SiGec layer of about        7E19 Atoms/cc

C. Non-Limiting Example Embodiments

The example embodiments can be combined with other stress or straininducing techniques such as stress memorization, dual stress layers(e.g, SiN capping stress layers). metal gates, STI stressors, etc.

Other configurations of gate structures are possible for allembodiments.

Given the variety of embodiments of the present invention justdescribed, the above description and illustrations show not be taken aslimiting the scope of the present invention defined by the claims.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention. It isintended to cover various modifications and similar arrangements andprocedures, and the scope of the appended claims therefore should beaccorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements and procedures.

What is claimed is:
 1. A device comprising: a substrate having a deviceregion; a p-type transistor on the device region of the substrate,wherein the transistor comprises a gate, source and drain (S/D) regionsadjacent to the gate, wherein a bottom of the S/D regions is disposedbelow a bottom of source-drain extension (SDE) regions, and a channelregion under the gate between the S/D regions; at least one recess inthe substrate; and a stressor region disposed in at least a portion ofthe recess in the substrate to apply a stress on the channel region, thestressor region comprises a carbon doped silicon germanium (SiGe)stressor layer having EOR defects, wherein a bottom of the stressorlayer is disposed at least below the EOR defects, and wherein the carbondoped SiGe stressor layer comprises an amount of carbon which reducesthe amount of EOR defects in order to reduce relaxation of the stress inthe stressor layer.
 2. The device of claim 1 wherein the at least onerecess in the substrate comprises S/D recesses adjacent to the gate. 3.The device of claim 2 wherein the carbon doped SiGe layer is disposed inat least a portion of the S/D recesses adjacent to the gate.
 4. Thedevice of claim 3 further comprises S/D layers above the carbon dopedSiGe layer in the S/D recesses.
 5. The device of claim 2 wherein thestress comprises a compressive stress.
 6. The device of claim 1 whereinthe at least one recess comprises a first recess and the carbon dopedSiGe layer completely occupies the first recess in the substrate.
 7. Thedevice of claim 6 wherein: the stressor region is disposed under andspaced apart from the channel region; and comprising a channel layerover the stressor region.
 8. The device of claim 7 wherein the at leastone recess comprises at least second and third recesses in thesubstrate, wherein the second and third recesses comprise S/D recessesadjacent to the gate.
 9. The device of claim 1 wherein the amount ofcarbon in the carbon doped SiGe layer comprises about 0.1 to 0.2 atomic%.
 10. The device of claim 1 wherein the bottom of the stressor layer isdisposed completely below the EOR defects.
 11. A device comprising: asubstrate having a device region; at least one transistor on the deviceregion of the substrate, wherein the at least one transistor comprises ap-type transistor, wherein the p-type transistor comprises a gate,source and drain (S/D) regions adjacent to the gate, wherein a bottom ofthe S/D regions is disposed below a bottom of source-drain extension(SDE) regions, and a channel region under the gate between the sourceand drain regions; at least one recess disposed in the substrate; and astressor region disposed in at least a portion of the recess in thesubstrate to apply a stress on the channel region, the stressor regioncomprises a carbon doped silicon germanium (SiGe) stressor layer havingEOR defects to form the S/D regions, and wherein a bottom of thestressor layer is disposed at least below the EOR defects.
 12. A devicecomprising: a substrate having a device region; at least one transistoron the device region, wherein the at least one transistor comprises agate, and diffusion regions adjacent to the gate, wherein a bottom ofthe diffusion regions is below a bottom of extension regions; at leastone recess disposed in at least a portion of the substrate; and astressor region in at least a portion of the recess to apply a stress ona desired region of the substrate, the stressor region comprises acarbon doped silicon germanium (SiGe) stressor layer having EOR defects,and wherein the carbon doped SiGe stressor layer comprises an amount ofcarbon to reduce the amount of EOR defects in order to reduce relaxationof the stress in the stressor layer and a bottom of the stressor layeris disposed at least below the EOR defects.
 13. The device of claim 12wherein the transistor comprises a channel region under the gate betweenthe diffusion regions and the desired region comprises the channelregion.
 14. The device of claim 12 wherein the at least one recess inthe substrate comprises S/D recesses adjacent to the gate.
 15. Thedevice of claim 14 wherein the at least one transistor comprises ap-type transistor.
 16. The device of claim 12 wherein the amount ofcarbon in the stressor layer comprises about 0.1 to 0.2 atomic %. 17.The device of claim 12 further comprises at least one diffusion layerdisposed above a top surface of the stressor layer, and wherein thetransistor comprises a n-type transistor.
 18. The device of claim 12wherein the at least one recess comprises a first recess and the carbondoped SiGe layer completely occupies the first recess in the substrate.19. The device of claim 18 wherein: the stressor region is disposedunder and spaced apart from the channel region; and comprising a channellayer over the stressor region.
 20. The device of claim 19 wherein theat least one recess comprises at least second and third recesses in thesubstrate, wherein the second and third recesses comprise S/D recessesadjacent to the gate.